The present invention relates to a high speed laser perforation system, and more particularly to a system employing a novel web feed-through mechanism and laser focusing system to achieve a higher rate of web perforation.
In order to affect the porosity and optical characteristics of web materials, laser systems are often employed to perform high resolution perforation of the webs. Laser systems are quite effective for this purpose because of the minute spacing between holes that can be achieved. For example, laser systems may be operated to form holes in web materials with spacings as low as 0.050 inches between holes.
Existing laser perforation systems typically employ some sort of scanning system or galvo system, utilizing rotatable mirrors, to move the laser beam across the web in a predetermined pattern. However, particularly for relatively wide webs, scanning and galvo systems have significant limitations in the speed at which they are able to move the laser beam across the web while performing high resolution perforation. These limitations are due to the relatively long distance between the focusing lenses and the workpiece for relatively wide webs, and performance requirements of laser perforation systems are dependent on the size of the holes to be formed as well as the required accuracy of hole placement and spacing. For example, conventional galvo systems experience speed limitations for web perforation operations involving 12-20 inch webs having holes with a size of about 10 thousandths of an inch, and for applications involving 2-3 inch webs having holes with a size of about 2-5 thousandths of an inch. Therefore, there is a need in the art for an improved, alternative system for high speed laser perforation of webs that overcomes the deficiencies of existing technology.
The present invention is an apparatus and method for high speed laser perforation of a web. A web-bearing cylinder receives the web in a wrapped spiral pattern, and includes a slit along a circular circumference of the cylinder. A laser guiding tube is provided for propagation of a laser beam within the web-bearing cylinder. An inner cylinder is also provided in the web-bearing cylinder. The inner cylinder has an axis, supports a reflecting mirror adjacent to the laser guiding tube to direct the laser beam in the slit in the web-bearing cylinder, and is rotatable around the axis to adjust an orientation of the reflecting mirror and thereby direct the laser beam around the circular circumference of the web-bearing cylinder in the slit.